The present invention relates to irradiated, oxidized olefin polymer dispersing aids for use in the manufacture of additive concentrates and additive-containing olefin polymer compositions.
The effective use of olefin-based polymers often requires the incorporation of additives into the polymer composition to enhance the polymer""s performance, aesthetic appeal and/or impart desirable properties. For example, pigments are often added to meet aesthetic requirements, or to improve heat resistance, heat absorption, and fade resistance. Halogenated flame retardants may be incorporated to improve flame-retardancy in the end-use product. Other additives, such as anti-acids, anti-microbial agents, and conductive carbon black are also often included in polymer compositions.
Improving the dispersion of additives in polymer compositions enhances the performance of those additives. In U.S. Pat. No. 6,384,148, oxidates of polyethylene produced using metallocene catalysts have been disclosed for the dispersion of pigments. In U.S. Pat. No. 5,079,283, organic peroxides and azo compounds were used to promote propylene polymer scission in polypropylene-based compositions containing flame retardants. The resulting higher melt flow material possessed improved flame retardancy. Still another approach to dispersion is to use polyethylene waxes, however, these compounds can result in polymer blooming, and an associated decrease in the useful life of products made from the polymer. Thus, there continues to be a need for improved dispersion of additives in olefin polymer compositions.
The dispersion of additives in olefin polymer compositions using the irradiated, oxidized olefin polymer dispersants of this invention provides a more homogenous distribution of the additive, and promotes desirable flexibility in the formulation of commercial olefin polymer materials. For example, at the same additive concentration, an olefin polymer composition containing an additive dispersed therein using the irradiated, oxidized polymer dispersants of this invention provides improved performance over the same olefin polymer composition without the dispersants of this invention. Alternately, a polymer manufacturer could take advantage of the performance enhancement provided by the irradiated, oxidized polymer dispersants of this invention, by reducing the additive levels in the olefin polymer compositions containing the dispersants, while maintaining equivalent additive performance of the same olefin polymer composition containing higher additive levels without the dispersants of this invention.
The irradiation of olefin polymers has been described in a number of patents. For example, U.S. Pat. No. 5,688,839 discloses irradiating colored olefin polymer resin particles and mixing the irradiated, colored resin particles with a background component, where the colored resin particles only partially disperse, so as to impart a marbleized appearance. U.S. Pat. No. 5,508,319 discloses the irradiation of polyethylene. U.S. Pat. Nos. 5,508,318, 5,554,668, 5,731,362, and 5,591,785 disclose irradiated propylene polymer material having long chain branching, high melt strength, and strain hardening elongational viscosity. U.S. Pat. Nos. 5,820,981 and 5,804,304 disclose a polymer that is subjected to irradiation in the substantial absence of oxygen, followed by a multistage treatment in the presence of a controlled amount of oxygen. However, none of these references disclose irradiated, oxidized olefin polymer dispersing aids for use in the manufacture of additive concentrates and additive-containing olefin polymer compositions. It has unexpectedly been found that the dispersants of the present invention provide distinct advantages in the dispersion of additives in olefin polymer compositions.
In one embodiment, the present invention relates to an additive-containing olefin polymer composition comprising:
A. 2.0 to 30.0 wt % of an irradiated, oxidized olefin polymer material;
B. 0.1 to 40.0 wt % of an additive selected from the group consisting of colorants, halogenated flame retardants, conductive carbon black, anti-microbial agents, anti-acids and mixtures thereof; and
C. 30.0 to 97.9 wt % of a non-irradiated, non-oxidized olefin polymer material;
wherein the sum of components A+B+C is equal to 100 wt %.
In another embodiment, the present invention relates to an additive concentrate composition, the composition comprising:
A. 9.0 to 85.0 wt % of an additive selected from the group consisting of colorants, halogenated flame retardants, conductive carbon black, anti-microbial agents, anti-acids and mixtures thereof; and
B. 15 to 91 wt % of an irradiated, oxidized olefin polymer material;
wherein the sum of components A+B is equal to 100 wt %.
Suitable olefin polymers useful as the irradiated and oxidized or non-irradiated and non-oxidized olefin polymers are propylene polymer materials, ethylene polymer materials, butene-1 polymer materials, and mixtures thereof.
When a propylene polymer material is used as the non-irradiated and non-oxidized olefin polymer material or as the starting material for making the irradiated, oxidized olefin polymer of the present invention, the propylene polymer material can be:
(A) a crystalline homopolymer of propylene having an isotactic index greater than 80%, preferably about 90% to about 99.5%;
(B) a crystalline random copolymer of propylene and an olefin selected from the group consisting of ethylene and C4-C10 xcex1-olefins, provided that when the olefin is ethylene, the maximum polymerized ethylene content is 10% by weight, preferably about 4%, and when the olefin is a C4-C10 xcex1-olefin, the maximum polymerized content thereof is 20% by weight, preferably about 16%, the copolymer having an isotactic index greater than 60%, preferably at least 70%;
(C) a crystalline random terpolymer of propylene and two olefins selected from the group consisting of ethylene and C4-C8 xcex1-olefins, provided that the maximum polymerized C4-C8 xcex1-olefin content is 20% by weight, preferably about 16%, and when ethylene is one of the olefins, the maximum polymerized ethylene content is 5% by weight, preferably about 4%, the terpolymer having an isotactic index greater than 85%;
(D) an olefin polymer composition comprising:
(i) about 10 parts to about 60 parts by weight, preferably about 15 parts to about 55 parts, of a crystalline propylene homopolymer having an isotactic index at least 80%, preferably about 90 to about 99.5%, or a crystalline copolymer selected from the group consisting of (a) propylene and ethylene, (b) propylene, ethylene and a C4-C8 xcex1-olefin, and (c) propylene and a C4-C8 xcex1-olefin, the copolymer having a propylene content of more than 85% by weight, preferably about 90% to about 99%, and an isotactic index greater than 60%;
(ii) about 3 parts to about 25 parts by weight, preferably about 5 parts to about 20 parts, of a copolymer of ethylene and propylene or a C4-C8 xcex1-olefin that is insoluble in xylene at ambient temperature; and
(iii) about 10 parts to about 80 parts by weight, preferably about 15 parts to about 65 parts, of an elastomeric copolymer selected from the group consisting of (a) ethylene and propylene, (b) ethylene, propylene, and a C4-C8 xcex1-olefin, and (c) ethylene and a C4-C8 xcex1-olefin, the copolymer optionally containing about 0.5% to about 10% by weight of a diene, and containing less than 70% by weight, preferably about 10% to about 60%, most preferably about 12% to about 55%, of ethylene and being soluble in xylene at ambient temperature and having an intrinsic viscosity of about 1.5 to about 4.0 dl/g;
the total of (ii) and (iii), based on the total olefin polymer composition being from about 50% to about 90%, and the weight ratio of (ii)/(iii) being less than 0.4, preferably 0.1 to 0.3, wherein the composition is prepared by polymerization in at least two stages;
(E) a thermoplastic olefin comprising:
(i) about 10% to about 60%, preferably about 20% to about 50%, of a propylene homopolymer having an isotactic index at least 80%, preferably 90-99.5% or a crystalline copolymer selected from the group consisting of (a) ethylene and propylene, (b) ethylene, propylene and a C4-C8 xcex1-olefin, and (c) ethylene and a C4-C8 xcex1-olefin, the copolymer having a propylene content greater than 85% and an isotactic index of greater than 60%;
(ii) about 20% to about 60%, preferably about 30% to about 50%, of an amorphous copolymer selected from the group consisting of (a) ethylene and propylene, (b) ethylene, propylene, and a C4-C8 xcex1-olefin, and (c) ethylene and a xcex1-olefin, the copolymer optionally containing about 0.5% to about 10% of a diene, and containing less than 70% ethylene and being soluble in xylene at ambient temperature; and
(iii) about 3% to about 40%, preferably about 10% to about 20%, of a copolymer of ethylene and propylene or an xcex1-olefin that is insoluble in xylene at ambient temperature; and
(F) mixtures thereof.
When an ethylene polymer material is used as the non-irradiated and non-oxidized olefin polymer material or as the starting material for making the irradiated, oxidized olefin polymer of the present invention, the ethylene polymer material is selected from the group consisting of (a) homopolymers of ethylene, (b) random copolymers of ethylene and an alpha-olefin selected from the group consisting of C3-10 alpha-olefins having a maximum polymerized alpha-olefin content of about 20 wt %, preferably a maximum of about 16 wt %, by weight, (c) random terpolymers of ethylene and said alpha-olefins, provided that the maximum polymerized alpha-olefin content is about 20 wt %, preferably the maximum is about 16 wt %, by weight, and (d) mixtures thereof. The C3-10 alpha-olefins include the linear and branched alpha-olefins such as, for example, propylene, 1-butene, isobutylene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3,4-dimethyl-1-butene, 1-heptene, 3-methyl-1-hexene, 1-octene and the like.
When the ethylene polymer is an ethylene homopolymer, it typically has a density of 0.89 g/cm3 or greater, and when the ethylene polymer is an ethylene copolymer with a C3-10 alpha-olefin, it typically has a density of 0.91 g/cm3 or greater but less than 0.94 g/cm3. Suitable ethylene copolymers include ethylene/butene-1, ethylene/hexene-1, ethylene/octene-1 and ethylene/4-methyl-1-pentene. The ethylene copolymer can be a high density ethylene copolymer or a short chain branched linear low density ethylene copolymer (LLDPE), and the ethylene homopolymer can be a high density polyethylene (HDPE) or a low density polyethylene (LDPE). Typically the LLDPE and LDPE have densities of 0.910 g/cm3 or greater to less than 0.940 g/cm3 and the HDPE and high density ethylene copolymer have densities of greater than 0.940 g/cm3, usually 0.95 g/cm3 or greater. In general, ethylene polymer materials having a density from 0.89 to 0.97 g/cm3 are suitable for use in the practice of this invention. Preferably the ethylene polymers are LLDPE and HDPE having a density from 0.89 to 0.97 g/cm3.
When a butene-1 polymer material is used as the non-irradiated and non-oxidized olefin polymer material or as the starting material for making the irradiated, oxidized olefin polymer of the present invention, the butene-1 polymer material is selected from a normally solid, high molecular weight, predominantly crystalline butene-1 polymer material selected from the group consisting of:
(1) a homopolymer of butene-1;
(2) a copolymer or terpolymer of butene-1 with a non-butene alpha-olefin comonomer content of 1-15 mole %, preferably 1-10 mole %; and
(3) mixtures thereof.
Typically the non-butene alpha-olefin comonomer is ethylene, propylene, a C5-8 alpha-olefin or mixtures thereof.
The useful polybutene-1 homo or copolymers can be isotactic or syndiotactic and have a melt flow rate (MFR) from about 0.5 to 150, preferably from about 0.5 to 100, and most preferably from 0.5 to 75 g/10 min.
These poly-1 -butene polymers, their methods of preparation, and their properties are known in the art. An exemplary reference containing additional information on polybutylene-1 is U.S. Pat. No. 4,960,820, the disclosures of which are incorporated herein by reference.
Suitable polybutene-1 polymers can be obtained, for example, by Ziegler-Natta low-pressure polymerization of butene-1, e.g. by polymerizing butene-1 with catalysts of TiCl3 or TiCl3xe2x80x94AlCl3 and Al(C2H5)2Cl at temperatures of 10-100xc2x0 C., preferably 20-40xc2x0 C., e.g., according to the process described in DE-A-1,570,353. It can also be obtained, for example, by using TiCl4xe2x80x94MgCl2 catalysts. High melt indices are obtainable by further processing of the polymer by peroxide cracking or visbreaking, thermal treatment or irradiation to induce chain scissions leading to a higher MFR material.
Preferably, the polybutene-1 contains up to 15 mole % of copolymerized ethylene or propylene, but more preferably it is a homopolymer, for example, Polybutene PB0300 homopolymer marketed by Basell USA Inc. This polymer is a homopolymer with a melt flow of 11 g/10 min. at 230xc2x0 C. and 2.16 kg and a weight average molecular weight of 270,000 dalton.
Preferably, the polybutene-1 homopolymer has a crystallinity of at least 55% by weight measured with wide-angle X-ray diffraction after 7 days. Typically the crystallinity is less than 70%, preferably less than 60%.
The non-irradiated, non-oxidized olefin polymer material and the starting material for the irradiated and oxidized olefin polymer material can be the same or different from each other.
The olefin polymer starting material for the irradiated, oxidized olefin polymer is exposed to high-energy ionizing radiation under a blanket of inert gas, preferably nitrogen. The ionizing radiation should have sufficient energy to penetrate the mass of polymer material being irradiated to the extent desired. The ionizing radiation can be of any kind, but preferably includes electrons and gamma rays. More preferred are electrons beamed from an electron generator having an accelerating potential of 500-4,000 kilovolts. Satisfactory results are obtained at a dose of ionizing radiation of about 0.1 to about 15 megarads (xe2x80x9cMradxe2x80x9d), preferably about 0.5 to about 9.0 Mrad.
The term xe2x80x9cradxe2x80x9d is usually defined as that quantity of ionizing radiation that results in the absorption of 100 ergs of energy per gram of irradiated material regardless of the source of the radiation using the process described in U.S. Pat. No. 5,047,446. Energy absorption from ionizing radiation is measured by the well-known convention dosimeter, a measuring device in which a strip of polymer film containing a radiation-sensitive dye is the energy absorption sensing means. Therefore, as used in this specification, the term xe2x80x9cradxe2x80x9d means that quantity of ionizing radiation resulting in the absorption of the equivalent of 100 ergs of energy per gram of the polymer film of a dosimeter placed at the surface of the olefin material being irradiated, whether in the form of a bed or layer of particles, or a film, or a sheet.
The irradiated olefin polymer material is then oxidized in a series of steps. The first treatment step consists of heating the irradiated polymer in the presence of a first controlled amount of active oxygen greater than 0.004% by volume but less than 15% by volume, preferably less than 8% by volume, more preferably less than 5% by volume, and most preferably from 1.3% to 3.0% by volume, to a first temperature of at least 25xc2x0 C. but below the softening point of the polymer, preferably about 25xc2x0 C. to 1400,more preferably about 25xc2x0 C. to 100xc2x0 C., and most preferably about 40xc2x0 C. to 80xc2x0 C. Heating to the desired temperature is accomplished as quickly as possible, preferably in less than 10 minutes. The polymer is then held at the selected temperature, typically for about 5 to 90 minutes, to increase the extent of reaction of the oxygen with the free radicals in the polymer. The holding time, which can be determined by one skilled in the art, depends upon the properties of the starting material, the active oxygen concentration used, the irradiation dose, and the temperature. The maximum time is determined by the physical constraints of the fluid bed.
In the second treatment step, the irradiated polymer is heated in the presence of a second controlled amount of oxygen greater than 0.004% by volume but less than 15% by volume, preferably less than 8% by volume, more preferably less than 5% by volume, and most preferably from 1.3% to 3.0% by volume to a second temperature of at least 25xc2x0 C. but below the softening point of the polymer. Preferably, the second temperature is from 100xc2x0 C. to less than the softening point of the polymer, and greater than the first temperature of the first step. The polymer is then held at the selected temperature and oxygen concentration conditions, typically for about 90 minutes, to increase the rate of chain scission and to minimize the recombination of chain fragments so as to form long chain branches, i.e., to minimize the formation of long chain branches. The holding time is determined by the same factors discussed in relation to the first treatment step.
In the optional third step, the oxidized olefin polymer material is heated under a blanket of inert gas, preferably nitrogen, to a third temperature of at least 80xc2x0 C. but below the softening point of the polymer, and held at that temperature for about 10 to about 120 minutes, preferably about 60 minutes. A more stable product is produced if this step is carried out. It is preferred to use this step if the irradiated, oxidized olefin polymer material is going to be stored rather than used immediately, or if the radiation dose that is used is on the high end of the range described above. The polymer is then cooled to a fourth temperature of about 70xc2x0 C. over a period of about 10 minutes under a blanket of inert gas, preferably nitrogen, before being discharged from the bed. In this manner, stable intermediates are formed that can be stored at room temperature for long periods of time without further degradation.
The preferred method of carrying out the treatment is to pass the irradiated polymer through a fluid bed assembly operating at a first temperature in the presence of a first controlled amount oxygen, passing the polymer through a second fluid bed assembly operating at a second temperature in the presence of a second controlled amount of oxygen, and then maintaining the polymer at a third temperature under a blanket of nitrogen, in a third fluid bed assembly. In commercial operation, a continuous process using separate fluid beds for the first two steps, and a purged, mixed bed for the third step is preferred. However, the process can also be carried out in a batch mode in one fluid bed, using a fluidizing gas stream heated to the desired temperature for each treatment step. Unlike some techniques, such as melt extrusion methods, the fluidized bed method does not require the conversion of the irradiated polymer into the molten state and subsequent re-solidification and comminution into the desired form. The fluidizing medium can be, for example, nitrogen or any other gas that is inert with respect to the free radicals present, e.g., argon, krypton, and helium.
As used in this specification, the expression xe2x80x9croom temperaturexe2x80x9d or xe2x80x9cambientxe2x80x9d temperature means approximately 25xc2x0 C. The expression xe2x80x9cactive oxygenxe2x80x9d means oxygen in a form that will react with the irradiated olefin polymer material. It includes molecular oxygen, which is the form of oxygen normally found in air. The active oxygen content requirement of this invention can be achieved by replacing part or all of the air in the environment by an inert gas such as, for example, nitrogen.
The concentration of peroxide groups formed on the polymer can be controlled easily by varying the radiation dose during the preparation of the irradiated polymer and the amount of oxygen to which such polymer is exposed after irradiation. The oxygen level in the fluid bed gas stream is controlled by the addition of dried, filtered air at the inlet to the fluid bed. Air must be constantly added to compensate for the oxygen consumed by the formation of peroxides in the polymer.
The irradiated, oxidized olefin polymer material of the invention contains peroxide linkages that degrade during compounding to form various oxygen-containing polar functional groups, e.g., acids, ketones and esters. In addition, the number average and weight average molecular weight of the irradiated, oxidized olefin polymer is usually much lower than that of the corresponding olefin polymer used to prepare same, due to the chain scission reactions during irradiation and oxidation.
Preferably, the non-irradiated and non-oxidized olefin polymer and the starting material for making the irradiated, oxidized olefin polymer material is a propylene polymer material, more preferably a propylene homopolymer having an isotactic index greater than 80%.
Suitable additives include colorants, halogenated flame retardants, anti-microbial agents, anti-acids, conductive carbon black and mixtures thereof Typically these additives have a particle size of less than 5 micron.
In the additive-containing olefin polymer composition, the additives can be present in an amount from 0.1 to 40 wt %, preferably 0.1 to 30 wt %, more preferably 0.3 to 12%. The irradiated, oxidized olefin polymer material can be present in an amount from 2.0 to 30.0 wt %, preferably 2.0 to 25 wt %, more preferably 2.0 to 20 wt %. The balance of the composition up to 100 wt % is the non-irradiated, non-oxidized olefin polymer material.
When the additive is a colorant, the colorant is preferably present in an amount from 0.1 to 5 wt %, more preferably 0.3 to 1.5 wt %. Typical examples include those organic or inorganic pigments commonly used with polyolefins such as carbon black, titanium oxide, graphite or color index (C.I.) pigment yellow series 62, 139, 151, 155, 169, 180, 181, 191, 194; C.I. pigment red series 122, 144, 149, 170, 175, 176, 185, 187, 209, 214, 242, 247, 262, 48:2, 48:3, 53:1, 57:1; C.I. pigment orange series 38,43, 68, 72; C.I. pigment violet series 19, 23; C.I. pigment blue series 15:1, 15:3, 15:4; C.I. pigment brown series 25 and 41, C.I. pigment green series 7, and phthalocyanine blue. The irradiated, oxidized olefin polymer material is preferably present in an amount from 2 to 30 wt %, more preferably 2 to 20 wt %. The balance of the composition is the non-irradiated, non-oxidized olefin polymer material.
When the additive is a halogenated flame retardant composition, the flame retardant composition includes a halogenated compound first component and a second component that interacts with the halogenated compound to form an intermediate compound. The halogenated compounds can include, for example, aliphatic, cycloaliphatic and aromatic bromine or chlorine compounds, such as tetrachlorobisphenol A, dibromopentaerythritol, hexabromocyclododecane, octabromodiphenyl ether, decabromodiphenyl ether (pentabromophenyl ether), hexabromobenzene, poly(tribromostyrene), pentabromodiphenyl ether, tribromophenyl-allyl ether, ethylene bis(tribromophenyl ether), bis(dibromopropyl)ether of tetrabromobisphenol A, tetrabromobisphenol A, tetrabromophthalic anhydride, dibromoneopentylglycol, and poly(dibromophenylene oxide). The second component can include compounds such as antimony trioxide, boron compounds, tin oxide, zinc oxide, zinc borate, aluminum trioxide, aluminum trihydroxide and mixtures thereof. The halogenated compound first component is preferably present in an amount from 2.0 to 30 wt %, more preferably from 2.0 to 20 wt %, most preferably 2.0 to 10 wt %. The second component is preferably present in an amount from 0.5 to 10 wt %, more preferably 0.5 to 7.0 wt %, most preferably 0.5 to 3 wt %. The irradiated, oxidized olefin polymer material is preferably present in an amount from 2.0 to 30.0 wt %, more preferably 2 to 25 wt %, most preferably 2 to 20 wt %. The balance of the composition is the non-irradiated, non-oxidized olefin polymer material.
Typical anti-acids include calcium stearate, hydrotalcite, zinc stearate, calcium oxide, and sodium stearate. Typical anti-microbial agents include compounds such as silver oxide.
The non-irradiated, non-oxidized olefin polymer material, additives, and irradiated, oxidized olefin polymer material can be combined at ambient temperature in conventional operations well known in the art; including, for example, drum tumbling, or with low or high speed mixers. The resulting composition is then compounded in the molten state to disperse the additive in any conventional manner well known in the art, in batch or continuous mode; for example, by using a Banbury mixer, a kneading machine, or a single or twin screw extruder. The material can then be pelletized.
When producing an additive concentrate, the additive is present in an amount from 9.0 to 85.0 wt %, preferably 9.0 to 40.0 wt %, more preferably 9 to 15 wt %. The balance of the composition up to 100 wt % is the irradiated, oxidized olefin polymer material.
When producing an additive concentrate where the additive is a colorant, the colorant is preferably present in an amount from 10 to 70 wt %, more preferably 10 to 55 wt %. Suitable types of colorants are as described above.
When producing an additive concentrate where the additive is a halogenated flame retardant composition, the halogenated compound first component is preferably present in an amount from 7.0 to 65 wt %, more preferably from 7.0 to 60 wt %. The second component is preferably present in an amount from 2.0 to 20 wt %. The balance of the concentrate is the irradiated, oxidized olefin polymer material. Typical types of the first and second components of the halogenated flame retardant composition are as described above.
The irradiated, oxidized olefin polymer material and additives can be combined and compounded in the manner as described above.